Lubricating composition

ABSTRACT

The present invention provides a lubricating composition comprising: (i) a base oil; (ii) a non-silicone anti-foam agent; and (iii) one or more performance additives; wherein the composition has a kinematic viscosity at 100° C. (according to ASTM D445) of 16.3 mm 2 /s or less, a low temperature cranking viscosity of at most 6600 cP at −30° C. (ASTM D5293) and a NOACK volatility of at most 11% according to CEC-L-40-93.

The present invention relates to a lubricating composition comprising abase oil and one or more performance additives for particular use in thecrankcase of an internal combustion engine, in particular an internalcombustion engine used in a passenger vehicle or light duty van.

In practice various lubricating compositions for crankcase engines areknown. A disadvantage of known crankcase engine oils is that, especiallywhen they are based on conventional mineral Group III base oils, theymay have undesirable fuel economy oil performance values, it beingproblematic to blend to lower SAE J300 viscosity grades. A furtherproblem of known crankcase engine oils is that they may have undesirableproperties for one or more of wear performance and NOACK volatility,particularly when blending to lower SAE J300 viscosity grades.

Attempts have been made to overcome the above problems by formulatingwith non-mineral oil Group III base oils, such as Fischer-Tropschderived base oils. WO2010020653 discloses the use of Fischer-Tropschbase oils in lubricating compositions. The composition of Example 1 ofWO2010020653 shows a surprisingly low NOACK volatility when compared tothe composition of Comparative Example 1 (using a Group III mineral baseoil).

However, it has been found that in low viscosity formulations such as0W-30 and 0W-40 engine oils, the use of Fischer-Tropsch base oils maynot be enough on their own to provide the low NOACK volatility valuesdesired for such formulations.

One way to further lower the NOACK volatility is to use a combination ofpolyalphaolefin base oils in addition to a Fischer-Tropsch derived baseoil. However, polyalphaolefin base oils are relatively expensive andtherefore it would be desirable to find an alternative way of loweringthe NOACK volatility of 0W-30 and 0W-40 formulations, particularly thoseformulations comprising Fischer-Tropsch derived base oils.

It has surprisingly been found that by including a non-siliconeanti-foam agent in the lubricating formulation the NOACK volatility canbe lowered to desirable levels.

Hence according to the present invention there is provided a lubricatingcomposition comprising:

(i) a base oil;(ii) a non-silicone anti-foam agent; and(iii) one or more performance additives;wherein the lubricating composition has a kinematic viscosity at 100° C.(according to ASTM D445) of 16.3 mm²/s or less, a low temperaturecranking viscosity of at most 6600 cP at −30° C. (ASTM D5293) and aNOACK volatility of at most 11% according to CEC-L-40-93.

According to another aspect of the present invention there is providedthe use of a non-silicone anti-foam agent for reducing the NOACKvolatility of a lubricating composition, in particular wherein thelubricating composition comprises a Fischer-Tropsch base oil.

Another important advantage of the present invention is that thelubricating composition has a desirably low cold-crank viscosity (i.e.dynamic viscosity according to ASTM D 5293), i.e. a cranking viscosityof at most 6600 cP at −30° C. (ASTM D5293).

It is an advantage of the present invention that it allows theformulation of alternative SAE J300 0W-30 and 0W-40 crankcase engineoils.

There are no particular limitations regarding the base oil used in thelubricating composition according to the present invention, and variousconventional mineral oils, synthetic oils as well as naturally derivedesters such as vegetable oils may be conveniently used, provided thatthe requirements in respect of the lubricant composition according tothe present invention are met.

The base oil used in the present invention may conveniently comprisemixtures of one or more mineral oils and/or one or more synthetic oils;thus, according to the present invention, the term “base oil” may referto a mixture containing more than one base oil. Mineral oils includeliquid petroleum oils and solvent-treated or acid-treated minerallubricating oil of the paraffinic, naphthenic, or mixedparaffinic/naphthenic type which may be further refined byhydrofinishing processes and/or dewaxing.

Suitable base oils for use in the lubricating oil composition of thepresent invention are Group III mineral base oils, Group IV poly-alphaolefins (PAOs), Group III Fischer-Tropsch derived base oils and mixturesthereof.

By “Group III” and “Group IV” base oils in the present invention aremeant lubricating oil base oils according to the definitions of AmericanPetroleum Institute (API) for category III and IV. These API categoriesare defined in API Publication 1509, 15th Edition, Appendix E, April2002.

Fischer-Tropsch derived base oils are known in the art. By the term“Fischer-Tropsch derived” is meant that a base oil is, or is derivedfrom, a synthesis product of a Fischer-Tropsch process. AFischer-Tropsch derived base oil may also be referred to as a GTL(Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oilsthat may be conveniently used as the base oil in the lubricatingcomposition of the present invention are those as for example disclosedin EP 0 776 959, EP 0 668 342, WO 97/21788, WO 00/15736, WO 00/14188, WO00/14187, WO 00/14183, WO 00/14179, WO 00/08115, WO 99/41332, EP 1 029029, WO 01/18156 and WO 01/57166.

Synthetic oils include hydrocarbon oils such as olefin oligomers(including polyalphaolefin base oils; PAOs), dibasic acid esters, polyolesters, polyalkylene glycols (PAGs), alkyl naphthalenes and dewaxed waxyisomerates. Synthetic hydrocarbon base oils sold by the Shell Groupunder the designation “Shell XHVI” (trade mark) may be convenientlyused.

Poly-alpha olefin base oils (PAOs) and their manufacture are well knownin the art. Suitable poly-alpha olefin base oils that may be used in thelubricating compositions of the present invention may be derived fromlinear C₂ to C₃₂, preferably C₆ to C₁₆, alpha olefins. Particularlypreferred feedstocks for said poly-alpha olefins are 1-octene, 1-decene,1-dodecene and 1-tetradecene.

Preferably, the base oil as used in the lubricating compositionaccording to the present invention comprises a Fischer-Tropsch derivedbase oil.

There is a strong preference for using a Fischer-Tropsch derived baseoil over a PAO base oil, in view of the high cost of manufacture of thePAOs. Thus, preferably, the base oil contains more than 50 wt. %,preferably more than 60 wt. %, more preferably more than 70 wt. %, evenmore preferably more than 80 wt. %. most preferably more than 90 wt. %Fischer-Tropsch derived base oil. In an especially preferred embodimentnot more than 5 wt. %, preferably not more than 2 wt. %, of the base oilis not a Fischer-Tropsch derived base oil. In a preferred embodimentherein, the lubricating composition is essentially free ofpolyalphaolefin base oil, i.e. no more than 2 wt. % of the base oil is apolyalphaolefin base oil. In a particularly preferred embodiment herein,the lubricating composition is free of polyalphaolefin base oil. Inanother preferred embodiment herein 100 wt % of the base oil is based onone or more Fischer-Tropsch derived base oils.

The total amount of base oil incorporated in the lubricating compositionof the present invention is preferably present in an amount in the rangeof from 60 to 99 wt. %, more preferably in an amount in the range offrom 65 to 90 wt. % and most preferably in an amount in the range offrom 70 to 85 wt. %, with respect to the total weight of the lubricatingcomposition.

According to the present invention the base oil (or base oil blend)preferably has a kinematic viscosity at 100° C. of at least 3.5 cSt(according to ASTM D445), preferably at least 3.8 cSt and mostpreferably at least 4.1 cSt.

The lubricating composition of the present invention further comprises anon-silicone anti-foam agent. As used herein the term “anti-foam agent”is a compound which is added into a lubricating composition at lowlevels (typically at a level of about 10 ppm to about 500 ppm) to helpdissipate surface air bubbles.

Preferably, the non-silicone anti-foam agent is selected from acrylate,polyacrylate, and polymethacrylate (PMA) polymers. A preferrednon-silicone anti-foam agent for use herein is a polyacrylate anti-foamagent. As used herein the term polyacrylate anti-foam agent includesalkyl polyacrylate anti-foam agents and acrylic copolymers.

The non-silicone anti-foam agent is preferably present at a level offrom 10 ppm to 500 ppm, preferably from 30 ppm to 200 ppm, morepreferably from 100 ppm to 200 ppm, by weight of the lubricatingcomposition.

An example of a suitable alkyl polyacrylate anti-foam agents is PC1644commercially available from Cytec. PC1644 is an acrylic copolymercomprising ethylacrylate and 2-ethylhexylacrylate copolymer. Anothercommercially available alkyl polyacrylate anti-foam agent for use hereinis PC2544 commercially available from Cytec. PC2544 is a modifiedacrylic copolymer.

As mentioned above, the lubricating composition according to the presentinvention meets certain specific requirements for the dynamic viscosityat −30° C., the kinematic viscosity at 100° C. and the NOACK volatility.

Typically, the dynamic viscosity at −30° C. (according to ASTM D 5293)of the composition is at most 6600 cP.

Typically, the dynamic viscosity at −35° C. (according to ASTM D 5293)of the composition is at most 6200 cP.

Typically, the kinematic viscosity at 100° C. (according to ASTM D 445)of the composition is at most 16.3 cSt, preferably from 9.3 to 16.3 cSt,more preferably from 9.3 and 12.5 cSt.

Typically, the high temperature, high shear viscosity (“HTHS”; accordingto ASTM D 4683) of the lubricating composition is in the range of from2.9 to 3.7 mPa·s, preferably in the range of from 2.9 to 3.5 mPa·s.

Typically, the NOACK volatility (according to CEC-L-40-93) of thecomposition is 11 wt % or below, preferably 10.5 wt % or below, evenmore preferably 10.0 wt. % or below. Typically the NOACK volatility(according to CEC-L-40-93) is at least 8 wt. %.

The lubricating composition according to the present invention furthercomprises one or more additives such as anti-oxidants, anti-wearadditives, dispersants, detergents, overbased detergents, extremepressure additives, friction modifiers, viscosity index improvers, pourpoint depressants, metal passivators, corrosion inhibitors,demulsifiers, anti-foam agents, seal compatibility agents and additivediluent base oils, etc.

As the person skilled in the art is familiar with the above and otheradditives, these are not further discussed here in detail. Specificexamples of such additives are described in for example Kirk-OthmerEncyclopedia of Chemical Technology, third edition, volume 14, pages477-526.

A preferred additive is a silicone-based anti-foam agent which can bepresent on its own or as part of a performance additive package. Thesilicone-based anti-foam agent is preferably present at a level of from20 to 200 ppm, by weight of the lubricating composition.

A preferred silicone-based anti-foam agent is a polysiloxane. Asilicone-based anti-foam agent is particularly useful herein incombination with a non-silicone anti-foam agent for providing alubricating composition having reduced NOACK volatility.

Anti-oxidants that may be conveniently used includephenyl-naphthylamines (such as “IRGANOX L-06” available from CibaSpecialty Chemicals) and diphenylamines (such as “IRGANOX L-57”available from Ciba Specialty Chemicals) as e.g. disclosed in WO2007/045629 and EP 1 058 720 B1, phenolic anti-oxidants, etc. Theteaching of WO 2007/045629 and EP 1 058 720 B1 is hereby incorporated byreference.

Anti-wear additives that may be conveniently used includezinc-containing compounds such as zinc dithiophosphate compoundsselected from zinc dialkyl-, diaryl- and/or alkylaryl-dithiophosphates,molybdenum-containing compounds, boron-containing compounds and ashlessanti-wear additives such as substituted or unsubstituted thiophosphoricacids, and salts thereof.

Examples of such molybdenum-containing compounds may convenientlyinclude molybdenum dithiocarbamates, trinuclear molybdenum compounds,for example as described in WO 98/26030, sulphides of molybdenum andmolybdenum dithiophosphate.

Boron-containing compounds that may be conveniently used include borateesters, borated fatty amines, borated epoxides, alkali metal (or mixedalkali metal or alkaline earth metal) borates and borated overbasedmetal salts.

The dispersant used is preferably an ashless dispersant. Suitableexamples of ashless dispersants are polybutylene succinimide polyaminesand Mannich base type dispersants.

The detergent used is preferably an overbased detergent or detergentmixture containing e.g. salicylate, sulphonate and/or phenate-typedetergents.

Examples of viscosity index improvers which may conveniently be used inthe lubricating composition of the present invention include thestyrene-butadiene stellate copolymers, styrene-isoprene stellatecopolymers and the polymethacrylate copolymer and ethylene-propylenecopolymers. Dispersant-viscosity index improvers may be used in thelubricating composition of the present invention.

Preferably, the composition contains at least 0.1 wt. % of a pour pointdepressant. As an example, alkylated naphthalene and phenolic polymers,polymethacrylates, maleate/fumarate copolymer esters may be convenientlyused as effective pour point depressants. Preferably not more than 0.3wt. % of the pour point depressant is used.

Furthermore, compounds such as alkenyl succinic acid or ester moietiesthereof, benzotriazole-based compounds and thiodiazole-based compoundsmay be conveniently used in the lubricating composition of the presentinvention as corrosion inhibitors.

Compounds which may be conveniently used in the lubricating compositionof the present invention as seal fix or seal compatibility agentsinclude, for example, commercially available aromatic esters.

The lubricating compositions of the present invention may beconveniently prepared by admixing the one or more additives, includingthe non-silicone anti-foam agent, with the base oil(s).

The above-mentioned additives are typically present in an amount in therange of from 0.01 to 35.0 wt. %, based on the total weight of thelubricating composition, preferably in an amount in the range of from0.05 to 25.0 wt. %, more preferably from 1.0 to 20.0 wt. %, based on thetotal weight of the lubricating composition.

Preferably, the composition contains from 10 wt. % to 15 wt. % of anadditive package comprising a combination of additives includinganti-oxidants, a zinc-based anti-wear additive, an ashless dispersant,an overbased detergent mixture, and a silicone-based anti-foaming agent.

According to an especially preferred embodiment of the presentinvention, the composition meets the requirements of an SAE J300 0W-30or 0W-40 formulation, preferably those of a 0W-30 formulation.

In another aspect, the present invention provides the use of anon-silicone anti-foam agent for reducing the NOACK volatility oflubricating composition, in particular wherein the lubricatingcomposition comprises a Fischer-Tropsch derived base oil.

Also the present invention provides a method of improving NOACKvolatility properties, which method comprises lubricating the crankcaseof an engine, in particular a passenger car motor engine, with alubricating composition according to the present invention.

The present invention is described below with reference to the followingExamples, which are not intended to limit the scope of the presentinvention in any way.

EXAMPLES Lubricating Oil Compositions

Various engine oils for use in a crankcase engine were formulated.

Table 1 indicates the properties for the base oils used.

TABLE 1 Base oil 1 Base oil 2 (GTL4) (GTL8) Kinematic viscosity at 4.28.5 100° C.¹ [cSt] VI Index² 120 120 NOACK volatility³ 14 5 [wt. %]¹According to ASTM D 445 ²According to ASTM D 2270 ³According to CECL-40-A-93/ASTM D 5800

Table 2 indicates the composition and properties of the fully formulatedengine oil formulations that were tested; the amounts of the componentsare given in wt. %, based on the total weight of the fully formulatedformulations.

All tested engine oil formulations contained a combination of a baseoil, an additive package (Additive Package 1), and a supplementaryadditive package (Additive Package 2), which additive packages were thesame in all tested compositions.

Additive package 1 was Infineum P6660 commercially available fromInfineum which contained a combination of additives includinganti-oxidants, a zinc-based anti-wear additive, an ashless dispersant,an overbased detergent mixture, and a silicone-based anti-foaming agent.

Additive package 2 contained a combination of a dispersant, anti-oxidantand a friction modifier.

Examples 1 to 6 contained a non-silicone anti-foam agent. Thenon-silicone anti-foam agents were alkyl polyacrylate anti-foam agentswith the tradenames PC1644 and PC2544 commercially available from Cytec.

Comparative Examples 2 to 4 contained a silicone-containing anti-foamagent (Synative AC AMH-2 commercially available from Cognis).

In all formulations, a conventional viscosity modifier concentrate wasused to adjust the viscosity and a conventional pour point depressantwas used to adjust the pour point.

“Base oil 1” was a Fischer-Tropsch derived base oil (“GTL 4”) having akinematic viscosity at 100° C. (ASTM D445) of approx. 4 cSt (mm²s⁻¹).

“Base oil 2” was a Fischer-Tropsch derived base oil (“GTL 8”) having akinematic viscosity at 100° C. (ASTM D445) of approx. 8 cSt (mm²s⁻¹).

These GTL 4 and GTL 8 base oils may be conveniently manufactured by theprocess described in e.g. WO-A-02/070631, the teaching of which ishereby incorporated by reference.

The compositions of Examples 1 to 6 and Comparative Example 1 to 4 wereobtained by mixing the base oils with the additive package and theanti-foam agent, where present, using conventional lubricant blendingprocedures.

The composition of Comparative Examples 1-4 and Examples 1-6 met therequirements of a 0W-30 formulation, according to SAE J300.

The lubricating compositions of the Examples and Comparative Exampleswere subjected to various test methods as indicated in Table 2 in orderto determine their NOACK volatility, their dynamic viscosity at −35° C.and their kinematic viscosity at 100° C. The results are shown in Table2.

TABLE 2 Comp. Comp. Comp. Comp. Component [wt. %] Ex. 1 Ex. 2 Ex. 3 Ex.4 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Additive Package 1 13.3 13.3 13.313.3 13.3 13.3 13.3 13.3 13.3 13.3 Additive Package 2 1.6 1.6 1.6 1.61.6 1.6 1.6 1.6 1.6 1.6 Pour Point Depressant 0.3 0.3 0.3 0.3 0.3 0.30.3 0.3 0.3 0.3 Viscosity Modifier 7.8 7.8 7.8 7.8 7.8 7.8 7.8 7.8 7.87.8 Synative AC AMH-2 — 0.003 0.01 0.02 — — — — — PC1644 — — — — 0.0030.01 0.02 — — — PC2544 — — — — — — — 0.003 0.01 0.02 GTL 4 71 71 71 7171 71 71 71 71 71 GTL 8 6 5.997 5.99 5.98 5.997 5.99 5.98 5.997 5.995.98 Total 100 100 100 100 100 100 100 100 100 100 Vk100¹ 12.06 12.0612.06 12.06 12.06 12.06 12.06 12.06 12.06 12.06 Vd-35² 6041 6041 60416041 6041 6041 6041 6041 6041 6041 NOACK³, %/m 11.5 11.4 11.2 11.1 10.110.3 9.9 10.7 10.2 10.1 ¹According to ASTM D445 ²According to ASTM D5293³According to CEC-L-40-93

DISCUSSION

As can be learned from Table 2, Examples 1-6 containing a non-siliconeanti-foam agent at 30 ppm, 100 ppm and 200 ppm, have significantly lowerNOACK volatility values than Comparative Examples 1-4 (not containingany non-silicone anti-foam agent).

An important advantage of the present invention is that 0W-30formulations meeting stringent NOACK volatility requirements (e.g. lessthan or equal to 10 wt. %) can be obtained without the need to use(relatively expensive) poly-alpha olefin (PAO) base oils.

1. A lubricating composition comprising: (i) a base oil; (ii) anon-silicone anti-foam agent; and (iii) one or more performanceadditives; wherein the composition has a kinematic viscosity at 100° C.(according to ASTM D445) of 16.3 mm²/s or less, a low temperaturecranking viscosity of at most 6600 cP at −30° C. (ASTM D5293) and aNOACK volatility of at most 11% according to CEC-L-40-93.
 2. Lubricatingcomposition according to claim 1, wherein the composition has a NOACKvolatility of at most 10.5% according to CEC-L-40-93.
 3. Lubricatingcomposition according to claim 1, wherein the non-silicone anti-foamagent is selected from acrylate, polyacrylate, and polymethacrylate(PMA) polymers.
 4. Lubricating composition according to claim 1, whereinthe non-silicone anti-foam agent is present at a level of from 10 ppm to500 pm, by weight of the composition.
 5. Lubricating compositionaccording to claim 1, wherein the base oil comprises one or moreFischer-Tropsch derived base oils.
 6. Lubricating composition accordingto claim 5, wherein the base oil comprises 80% or greater of one or moreFischer-Tropsch derived base oils, by weight of the base oil. 7.Lubricating composition according to claim 1, wherein the composition isessentially free of polyalphaolefin base oil.
 8. Lubricating compositionaccording to claim 1, wherein the one or more performance additivescomprises a silicone-based anti-foam agent.
 9. (canceled)
 10. (canceled)11. A method of lubrication comprising applying a lubricatingcomposition to a crankcase of an engine, wherein the lubricatingcomposition comprises: (i) a base oil; (ii) a non-silicone anti-foamagent; and (iii) one or more performance additives; wherein thecomposition has a kinematic viscosity at 100° C. (according to ASTMD445) of 16.3 mm²/s or less, a low temperature cranking viscosity of atmost 6600 cP at −30° C. (ASTM D5293) and a NOACK volatility of at most11% according to CEC-L-40-93.
 12. The method according to claim 11,wherein the non-silicone anti-foam agent is an alkyl polyacrylateanti-foam agent.
 13. The method according to claim 11, wherein thecomposition has a NOACK volatility of at most 10.5% according toCEC-L-40-93.
 14. The method according to claim 11, wherein thenon-silicone anti-foam agent is selected from acrylate, polyacrylate,and polymethacrylate (PMA) polymers.
 15. The method according to claim11, wherein the non-silicone anti-foam agent is present at a level offrom 10 ppm to 500 pm, by weight of the composition.
 16. The methodaccording to claim 11, wherein the base oil comprises one or moreFischer-Tropsch derived base oils.
 17. The method according to claim 11,wherein the base oil comprises 80% or greater of one or moreFischer-Tropsch derived base oils, by weight of the base oil.
 18. Themethod according to claim 11, wherein the composition is essentiallyfree of polyalphaolefin base oil.
 19. The method according to claim 11,wherein the one or more performance additives comprises a silicone-basedanti-foam agent.